Filter posts by category on frontpage wordpress 2.9+

functions.php

// =========================================
// = Filter posts by category on frontpage =
// =========================================

function exclude_category($query) {
  if ( $query->is_home() ) {
    $query->set('cat', '-6');
  }
  return $query;
}

add_filter('pre_get_posts', 'exclude_category');